Mcat Biology (Chapter 1)

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serial endosymbiosis theory

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attempts to explain the formation of some of the membrane-bound organelles; it posits that these organelles formed by the engulfing of one prokaryote by another and the establishment of a symbiotic relationship between the two; in addition to mitochondria, chloroplasts in plant cells and organelles of motility (such as flagella) are believed to have evolved through this process

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lysosomes

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membrane-bound structures containing hydrolytic enzymes that are capable of breaking down many different substrates, including substance ingested by endocytosis and cellular waste products

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autolysis

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release of lysosome enzymes; leads to degradation of cellular components and apoptosis

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endoplasmic reticulum (ER)

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made up of the rough ER (RER) and smooth ER (SER); contiguous with the nuclear envelope

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rough endoplasmic reticulum (RER)

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studded with ribosomes, which permit translation of proteins destined for secretion directly into its lumen

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smooth endoplasmic reticulum (SER)

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lack ribosomes; utilized for lipid synthesis and detoxification of certain drugs and poisons; transports proteins from RER to Golgi apparatus

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lumen

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inside space of tubular structure

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Golgi apparatus

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modifies, sorts and directs cellular products; modifies by the addition of various groups, including carbohydrates, phosphates, and sulfates

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peroxisomes

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contain hydrogen peroxide; breakdown very long chain fatty acids bio beta-oxidation; participate in synthesis of phospholipids; contain some of the enzymes involved in the pentose phosphate pathway

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cytoskeleton

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three components: microfilaments, microtubules and intermediate filaments

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microfilaments

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composed of actin; provide structural protection from the cell and can cause muscle contraction through interactions with myosin; help form the cleavage furrow during cytokinesis in mitosis

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microtubules

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composed of tubulin; create pathways for motor protein like kinesin and dynein to carry vesicles; contribute to structure of cilia and flegalla; pull apart sister chromatids during mitosis

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cilia

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projections from a cell that are primarily involved in movement of materials along the surface of the cell

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flagella

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structures involved in movement of the cell itself

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9 + 2 structure

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seen only in eukaryotic organelles of motility, such as cilia and flagella; composed of nine pairs of microtubules forming an outer ring, with two microtubules in the center

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intermediate filaments

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involved in cell-cell adhesion or maintenance of the integrity of the cytoskeleton; help anchor organelles;

ex: keratin, desmin

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4 types of tissue

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epithelial, connective, muscle and nervous tissue

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epithelial tissue

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covers the body and lines its cavities, protecting against pathogen invasion and desiccation (drying); form the parenchyma; cells tightly joined to each other and to an underlying layer of connective tissue known as the basement membrane

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parenchyma

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functional parts of organs

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simple epithelia

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one layer of epithelial cells

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stratified epithelia

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many layers of epithelial cells

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pseudostratified epithelia

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appear to have multiple layers of epithelial cells because of differences in cell heights, but actually have only one layer

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squamous cells

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flat and scalelike in shape

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connective tissue

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supports the body and provide a framework for epithelial cells; form the stroma or support structure by secreting materials v(collagen and elastin) to form an extracellular matrix

ex: bone, cartilage, tendons, ligaments, adipose tissue and blood

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three domains of life

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Archaea, Bacteria and Eukarya

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Archaea

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often extremophiles (live in high temperatures, high salinity, no light); use photosynthesis as well as alternative sources of energy like chemosynthesis (inorganic substances); similarities to both eukaryotes (start translation with methionine, similar RNA polymerases, histones) and bacteria (single circular chromosome, divide by binary fission or budding)

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Bacteria

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have many similar structures to eukaryotes, and have complex relationships with humans, including symbiosis (both benefit) and pathogenesis

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fimbriae

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similar to cilia; sometimes bacteria have this

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cocci

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sphrerical bacteria

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bacilli

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rod-shaped bacteria

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spirilli

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spiral-shaped bacteria

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obligate aerobes

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bacteria that require oxygen for metabolism

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obligate anaerobes

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bacteria that cannot survive in an oxygen-containing environment

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facultative anaerobes

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bacteria that can toggle between metabolic processes, using oxygen for aerobic metabolism if it is presents, and switching to anaerobic metabolism if it is not

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aerotolerant anaerobes

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bacteria which are unable to use oxygen for metabolism, but are not harmed by its presence in the environment

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envelope

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together the cell wall and cell membrane (plasma membrane) of bacteria are known as this

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Gram staining process

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determines type of cell wall in bacteria; a crystal violet stain is followed by a counterstain with a substance called safranin; envelope absorbs one of the two

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gram positive cell wall

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bacteria with envelope which absorbs the crystal violet stain and appears deep purple; contains peptidoglycan and lipoteichoic acid

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gram negative cell wall

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bacteria with envelope which absorbs the safranin and appears pink-red; contain peptidoglycan (in much smaller quantities than gram positive cell wall) and outer membrane containing phospholipids and lipopolysaccharides

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flagella

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composed of a filament, basal body and hook

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chemotaxis

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ability of a cell to detect chemical stimuli and move toward or away from them

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filament

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a hollow, helical structure composed of flagelling

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basal body

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complex structure that anchors the flagellum to the cytoplasmic membrane and is also the motor of the flagellum

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hook

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connects the filament and the basal body so that, as the basal body rotates, it exerts torque on the filament, which can thereby spin and propel the bacterium forward

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plasmids

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in prokaryotes; small circular structures on which DNA acquired from external sources may be carried; not necessary for survival of prokaryote but may give advantage

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virulence factors

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traits that increase how pathogenic a bacterium is such as toxin production, projections that allow the bacterium to attach to certain kinds of cells or evasions of the host's immune system

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episomes

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subset of plasmids that are capable of integrating into the genome of bacterium

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bacterial genetic recombination processes

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transformation, conjugation and transduction

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transformation

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results from the integration of foreign genetic material into the host genome

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conjugation

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bacterial form of mating (sexual reproduction)

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conjugation bridge

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during bacterial conjugation, this enables two cells to transfer genetic material from donor male (+) to recipient female (-)

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sex pili

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appendages which from the conjugation bridge during bacterial conjugation

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sex factors

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bacteria must contain these plasmids that contain the necessary genes in order to form sex pili

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F (fertility) factor

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sex factor (plasmid) in E. coli;

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F+ cells

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can transfer plasmid to F-

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Hfr cells

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can transfer portion of the genome to recipient because plasmid has gone transformation and been integrated into the host genome

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transduction

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only genetic recombination process that requires a vector

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vector

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a virus that carries genetics material from one bacterium to another

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bacteriophage

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virus that infects bacteria; has a capsid (protein coat), tail sheath and tail fibers

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transposon

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genetic elements capable of inserting and removing themselves from the genome; present in prokaryotes and eukaryotes

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bacteria growth phases

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1. lag phase

2. exponential or log phase

3. stationary phase

4. death phase

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tail sheath

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the part of bacteriophages that can act as a syringe, injecting genetic material into a bacterium

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tail fibers

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the part of bacteriophages that help it recognize and connect to the correct host cell

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obligate intracellular parasites

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viruses; means that they cannot survive and replicate outside of a host cell

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virions

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individual virus particles

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viral genomes

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either DNA or RNA and may be single or double stranded in both cases; circular or linear in shape

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positive sense RNA viruses

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the genome may be directly translated to functional proteins by the ribosomes of the host cell (just like mRNA)

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negative sense RNA viruses

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require synthesis of a complementary RNA strand first , which can then be used as a template for protein synthesis; must carry an RNA replicase in the virion to ensure the complementary strand is synthesized

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retroviruses

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enveloped, single-stranded RNA viruses; carry an enzyme called reverse transcriptase which synthesized DNA from single-stranded RNA; DNA is integrated into host cell's DNA (by integrase)

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lytic cycle

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bacteriophage makes maximal use of cell's machinery with little regard for the survival of the host cell; once host is swollen with new virions, the cell lyses

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virulent

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bacteria in the lytic phase

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lysogenic cycle

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virus integrates into the host genome as a provirus or prophage, which can then reproduce along with the cell; provirus then leaves the genome in response to a stimulus at some later time and lytic cycle

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prions

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infectious proteins; cause disease by triggering misfolding of other proteins from an alpha-helical structure to a beta-pleated sheet; reduces solubility of protein and ability of cell to degrade misfolded protein

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viroids

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small plant pathogens consisting of very short circular single-stranded RNA; silence genes in plant genome;